Smart Lighting Blog

Smart Lighting Blog: A forum to discuss issues and developments regarding outdoor lighting



21 thoughts on “Smart Lighting Blog

  1. Here’s an example of what happens when citizens become accustomed to glare and light trespass:

    Unfortunately the public often mistakenly equates bright glaring lights with increased visibility and safety. Adding fully shielded motion controlled path and entrance lighting of reasonable lighting level on their property will improve visibility and safety more efficiently. However after decades of street lights that blast lighting into yards, trees and bedrooms, people have grown accustomed to the light trespass and actually miss it. A really sad commentary on the effects of poor lighting design and the ingrained perception that glare makes people “feel safer”. The gentleman in the video clip also wrongly asserts that criminals always seek out the dark to operate. Car thieves and vandals often prey on cars that they can assess without using a flashlight. Thieves break into cars that they know have valuables worth stealing. Street lighting makes that assessment easier.

  2. Here’s a good example of the “feeling of safety” vs. actual safety regarding street lighting. Perception unfortunately becomes reality and not feeling safe causes the public to alter its behavior. We have to start lighting sidewalks for pedestrians using adaptive controls and motion sensors. Streets with speed limits less than 30 mph don’t need lighting because headlights already do a better job.

  3. Will “historic preservation” doom cities to a future of glaring, inefficient lighting that contributes to increased skyglow, CO2 and ecological damage? When did a plexiglass globe become a historic period fixture and why does anybody like it?

    As I speak to city planners I am dumbfounded regarding the affection for “acorn” lighting fixtures as well as the total cognitive dissonance that allows them to say energy efficient and acorn in the same sentence. While you can make them more efficient by changing them to LED, real energy efficiency, or efficacy comes from putting the lumens coming out of the fixture into a useful location, like a sidewalk. Even the best acorn fixtures do a miserable job at this task, blasting 20-30% of their lumens into the sky or your eyes. This might have been tolerable in the 1920’s when the original real fluted-glass versions appeared with incandescent lamps, but now some of these fixtures have 10x the lumen output.

    Photo credit Jim Richardson

    Yet, city after city announces new LED retrofits and replaces old monstrosities for newer monstrosities. A few manufacturers have been designing new historical pole top fixtures that look great and perform well, but historic preservation groups continue to veto them in favor of plexiglass globes…

    Here’s what a good pole top historical decorative looks like today:

    Isn’t it about time that we stop sabotaging the future by using fixtures that cause glare, harm wildlife and waste energy just because they vaguely look old-fashioned?

  4. What keeps cities from installing adaptive controls with LED retrofit projects?

    This is the Holy Grail of reducing total global lumens and there is no easy answer. What is becoming clear in my investigation is that how and where the decision is made in the management hierarchy matters. Most DOT staff seem to somewhat resistant to change. For decades the only real change that they have had to worry about was adopting newer types of lamps installed in familiar lighting fixtures. However in the few years they have seen more changes than the past couple generations combined. The lighting industry is evolving more like the computer industry and instant obsolescence is now a potential consequence.

    In addition, lighting standards are poised to be updated to reflect the lessons being learned in the field using SSL. Visibility with white light is much better and the obvious implication is that we don’t need as much light using LED as we did with HPS. However there is real concern that reducing lighting levels will be controversial with both the industry and the public. We can also anticipate “ambulance chaser” lawyers ready to use any change as a cause for negligence in accidents.

    When talking to the NYCDOT one year ago the ideal of reducing lighting levels was met with undisguised derision. I was told in no uncertain terms; “We never get complaints that the lighting is too bright. The public wants more, not less light.”

    When I mentioned that the IES RP-8, which the NYCDOT uses for their lighting practices, specifically allows for dimming lighting to meet the current vehicle and pedestrian volume, they said that they didn’t care. In fact, it became obvious that they did not realize that this was possible using the RP-8. They also said “This is New York, the city that never sleeps. Our traffic doesn’t change that much, so we don’t have to worry about it.”

    However, their final statement revealed what really drives the policies of the largest DOT in the world: fear. Fear of litigation. They would rather install 250,000 LED streetlights without adaptive controls than consider reducing lighting levels to the standards that they already profess to follow. They closed the meeting saying that one lawsuit could cost more than any possible savings from reducing energy. This is not true, but NYCDOT was not able to share any info regarding lawsuits that they have lost or settled out of court.

    What is disconcerting is this was almost verbatim what I heard from the Los Angeles Street Lighting Bureau when I met with them 5 years ago. They were already a year into their 140,000 LED streetlight retrofit. While adaptive controls were discussed, they decided that the technology was not mature enough at the time, which was probably true. However again the real reason that dimming was not considered was a pervasive belief that any reduction in lighting levels would cause an increase in crime and potentially expose the city to increased litigation. They also feared that the police department would not endorse any reduction in lighting levels and the project would never have been approved by the Mayor.

    So the future of public lighting will be less efficient, cost more and cause substantially more negative ecological consequences simply due to the fear of lawyers. If this was based on real litigation costs it might be more understandable. However, my investigation of the actual legal cases regarding outdoor lighting that have been won by the plaintiff, shows a completely different story. Most cases filed and being won or settled out of court involve poor maintenance. (i.e. burned out lamp) Legally once you choose to install public lighting you are held responsible when you don’t maintain it well. However I could find no cases that show a judgement levied against a city for not providing any lighting or providing it at an illuminance level lower than any standards body has set. In short, the fear of reducing lighting levels has no basis in legal precedence.

    This doesn’t stop cities from using it as an excuse and this coupled with a very real preference for more light by the majority of the public and police will likely retard the adoption of adaptive controls significantly. While SOLA is actively seeking funding to conduct research to document safety before and after a retrofit using dimming, the facts are not likely to have an immediate impact on acceptance of reduced lighting levels.

    The real tragedy is that installing adaptive controls makes sense today and pays for itself even if the city chooses not to dim after peak traffic periods.

    In addition to dimming after 10 pm, Cambridge, MA is also using the dimming capability to compensate for lumen depreciation of the LED fixture. The initial maximum light output for each fixture is reduced by 30%. As the fixture’s output declines due to normal lamp depreciation, the city can compensate by increasing the lighting level slightly. Using older HID technology, standard operating procedures was to install a lamp with more lumen output than was necessary initially so that it would have the desired brightness at the end of the lamp’s useful life. With adaptive controls and dimming it is possible to save 20% or more energy over the life of the fixture while dramatically extending life of the fixture. Reduced drive current also reduces heat which is the single biggest factor in lumen depreciation and component failure. Using this practice, LED fixtures being installed today could easily be working for 20 years or more.

    Coincidentally using the additional dimming for constant lumen output also pays for the cost of the adaptive controls installation. Another bonus is that if standards change, or the fear of litigation, the city can implement dimming in the future with the touch of a computer keyboard.

    Smart huh?

  5. This article on LED Retrofits in the UK shows the results of LED swaps without public outreach and education.

    “Had to use the light on my phone to get the key in the door! They are awful, very dangerous.”

    In this case the public is reacting to dramatically better beam control with LED that no longer spills light into the front yards and bedroom windows. However light trespass has become so commonplace with older lighting technology that when removed the public see it as a loss of security. Wouldn’t it be better for homeowners to install motion activated porch lights so that they don’t need to carry a flashlight?

    “Not only that, but when the lights are on there’s far too much of a gap between them so it would be very easy for a burglar or a mugger to sneak between them.”

    The UK has generally been installing new LED fixtures at minimum recommended illumination levels. However this has been a significant reduction in lighting levels in many places where overlighting has been prevalent. Again the public reaction has been shock at the lower lighting levels. They may have had more light between the poles with the older HID fixtures, but most of it would have been in the form of high-angle glare which has often been reduced significantly. This has actually increased visibility while using less light output. Unfortunately citizens often conflate glare with better safety.

    Overall this article points out the very real need for better educational outreach before retrofits are scheduled. While explaining visibility and real safety may be difficult, without the effort the public will often react with frustration.

    1. Bob,

      This is less about “educational outreach” and more about 1) giving the public the level and type of lighting which they actually want, and 2) specifying, designing and installing new lighting systems ‘properly’ and professionally.

      Neither of these things is happening in the UK – which is why there is so much resistance to LED street lighting.

  6. What will it take for cities to choose Smart Lighting?

    This is a new installment in the ongoing discussion of why more cities are not choosing to install adaptive controls in order to achieve maximum energy and CO2 reduction as a result of their LED retrofits.

    City governments and planners are by nature risk-adverse. Most would rather have someone else try something new if there is any potential uncertainty involved. Learning from your, or better yet others, mistakes is a sign of prudence and wisdom. So it is not surprising that many cities have chosen, and continue to choose, to sit on the sidelines or to go ahead with LED retrofits without dimming or adaptive controls.

    It has taken several years for the technology to mature and standardization has been slow to occur. With the explosive growth of the industry over the last few years, many believe that a significant shake out is inevitable. Philips Lighting has fueled this opinion with the recent spin off of Lumileds Lighting, and the planned split of its remaining business units into separate companies.

    Nobody wants to buy technology that is potentially obsolete and/or unsupported by the loss of a vendor. So when is the right time to make the jump? When the benefit outweighs the risk. When this point actually occurs is often difficult to discern and can be somewhat or totally subjective.

    Installing dimming-ready fixtures is now a complete no brainer. The cost is minimal, and the potential benefit of future flexibility makes it an easy decision. However, the controls themselves add real additional cost to the project, averaging 10-25%. Therefore, this is the point where some planners are drawing the line. If they don’t plan to dim now, why spend the money?

    I see two main reasons to perform the controls installation at the same time as the fixture: a) the significant additional labor and the associated disruption of retrofitting controls later; and b) they are is essentially free if you use initial dimming for constant lumen output over the life of the fixture.

    The cost of labor to install controls at the same time as the fixture is minuscule, so not doing so at the same time adds quite a bit to the total cost, which will also significantly extend the payback period. These factors may conspire to make the decision to leave the fixtures alone until replacement is required somewhat compelling, especially if you think that they may only last a decade.

    Fortunately, or unfortunately, the smart money is now on fixtures being installed today lasting for 20 years or more with relatively little maintenance. Furthermore, 20 years from now, we may easily find we were off by a decade or so. If the driver holds up or is easily replaced, the LEDs may only dim by 20% in 20 years. It is very likely that by that time, lighting standards will have evolved to recognize that the improved visibility of white light allows for across the board reduction of recommended illumination levels of 20-40%. Consequently, the projected life of the LEDs could last indefinitely and replacement of drivers or a few faulty LED arrays become a real option.

    However, this is the new no-brainer: initial dimming to 70-80% will compensate for projected lumen depreciation, and using the additional savings will pay for the controls in the same payback period. This is future proofing your investment. When standards change, you can change illumination levels with the touch of a keyboard. When the safety data is compiled which proves once and for all that using recommended illumination levels for the road classification — and dimming to match the changes in traffic during the night — have no impact on public safety, you can reduce those levels to save more money, energy and CO2.

    But the last and most vexing reason for foregoing dimming is that some utility companies won’t pass the energy conservation savings on to the customer. Most will adjust the pole rate down to reflect the lower energy consumption at full output, but may also adjust a maintenance fee upwards to offset much of the savings.

    Convincing utility companies to accept the energy consumption metering data from the controls software has yet to be accomplished. Accordingly, the very real potential loss of income from widespread LED and adaptive controls adoption now may reign as the major deterrent to saving 60-70% of the world’s energy and CO2. Can we really make this transition successfully without government leadership? The short answer, no. Only in areas where state or local regulation of the utilities have created incentives for energy conservation do we see some progress in the use of dimming. Without further regulation at the state or Federal level to require fair utility tariffs, the conversion to adaptive controls will likely be throttled.

  7. Crosswalks are too important to not properly light.

    This news reports points out a real problem in many cities. Defining a place to cross a street brings with it the responsibility to help pedestrians safely cross. Just drawing lines and putting up a sign doesn’t cut it at night. In fact the daughter of the victim in this report is exactly right. Defining a crosswalk gives pedestrians a false sense of safety and can contribute to more fatalities than if there was no crosswalk at all.

    The Federal Highway Administration (FHWA) and Virginia Tech Transportation Institute (VTTI) conducted research and produced a great guide for crosswalk design in 2008. “Informational Report on Lighting Design for Mid-block Crosswalks Publication No. FHWA-HRT-08-053” show the challenges of improving the visibility of pedestrians.

    Lighting Research Center has also produced a report for the FHWA:

    The reports also include new lighting designs that direct more of the light where it is needed so that drivers can see the pedestrian before its too late. Vertical illuminance is paramount, and lots of it. At a minimum, 20 lux should be used for mid-block and 30+ for intersections. But in all cases, it’s contrast that makes visibility possible.

    Only after adequate lighting and vertical illuminance is provided should flashing beacons or in pavement marker lights be considered. Installing these alone can actually become a distraction to the driver if the visibility of the pedestrian can’t compete with the warning lights.

    SOLA is seeking funding for an update to the current research that includes advances in technology like LED. The directionality of LED fixtures should make it easier to produce the needed vertical illuminance without the glare of the older HID fixtures. In addition, broad spectrum white light may improve visibility due to improved color contrast. One intriguing possibility to test is using in-pavement LED lighting that has white LEDs to illuminate the pedestrians and yellow to warn drivers. This research is high on our priority list and pedestrian scale lighting in general needs to become the focus of lighting standards for an urban environment.

  8. The Origin of the Washington Globe, AKA “acorn” fixture

    I recently met with the United States Commission of Fine Arts (CFA) which has statutory authority to review all the “design and aesthetics” of all construction within Washington, D.C. I met with them to discuss the Washington Globe streetlight fixture. As you may have read in an earlier entry to this blog (April 9,2015), I believe the Washington Globe, or “acorn” fixtures as they are generically called are one of the worst lighting fixtures in use today. I met with the CFA to see if they would consider approval of a new “period” LED pole top fixtures that are dramatically better at directing light onto the sidewalk, instead of into the sky and your eyes as glare.

    Prior to the meeting I researched the history of Washington Globe and found a few fascinating facts worth relaying.

    First as a matter of background, the CFA was established by Congress in 1910. One of the first tasks it undertook was to establish a design contest to create a streetlight standard. One of the founding CFA members, Francis Davis Millet, submitted the winning design and it was placed in service in 1911. Tragically, Millet died the following year when the Titanic sank.

    The original Washington Globe streetlight was made of fluted glass and boasted a 400 lumen incandescent bulb, or approximately the same output as the 40 watt incandescent used in many homes. The Washington Globe currently in use is 15 to 20 times brighter with approximately 40% of the energy being wasted as glare and uplight.

    In my discussion with the CFA it became clear that they are extremely devoted to the Washington Globe and won’t abide any change to the design. While they agree that it produces too much glare, they don’t like the use of an internal shield or external cap designed to reduce uplight and conserve energy. They prefer a fully illuminated globe. They do prefer a warmer white light source similar to the incandescent lamp that was originally used.

    So in order to preserve our historical past, the CFA is willing to accept the negative consequences of using the Washington Globe: wasted energy, increased CO2 and higher operating cost. The only real way that it could be improved under these restrictions is to reduce the lamp output and color temperature significantly. This would save energy and thanks to changes in the new IES recommended practices it can be accomplished. The IES RP-8-14 specifies that in neighborhoods with low pedestrian activity and speed limits of 30 mph or less, no additional road surface lighting is necessary. Research has shown that vehicle headlights alone do a better job of illuminating the road and seeing potential hazards. If the Washington, DC DOT (DDOT) were to reduce the brightness of the pole top fixtures by about 50% and direct it only to the sidewalk, a vast improvement in visibility and energy reduction can be made.

    But to achieve real energy reduction of approximately 70% of energy and CO2 for all streetlights, all cities should be adjusting the light output to match the RP-8 recommended illumination levels throughout the night. The IES criteria for lighting levels are based on pedestrian and vehicle traffic for the road. The higher the traffic, the higher the recommended lighting level. At rush hour most roads have their highest usage and by 10 pm that traffic level may have dropped so far that the recommended lighting level is half of what it was a few hours earlier.

    Older lighting technology like HPS wasn’t able to dim to a lower level, so by necessity illumination levels remained the same from dusk to dawn. New LED lighting can be fitted with adaptive controls that can vary the light output and can be programmed to reduce brightness after peak traffic levels subside. In Cambridge, MA they are doing this at 10 PM and reducing 77% of their energy and CO2.

    Will Washington, DC do this? Not unless the public and elected officials demand it. DDOT is considering the installation of adaptive controls with new LED streetlights, but has no plans for dimming at this time.

  9. Energy Saving Posers vs Real Energy Savings

    I have heard one too many press releases touting how green their city is because they switched to LED streetlights. Switching to LED may be a good start, but not if you continue to over light and don’t reduce lighting levels to meet the standards that you say you follow.

    Most international lighting recommendations (IES, CIE, etc.) specify lighting levels based on the quantity of traffic on the road at a specific time. So the amount of lighting needed at rush hour, is not the same amount that is needed at 2 AM almost everywhere on the planet.

    Why then do 95% of cities still maintain rush hour lighting levels dusk to dawn? Because they are afraid that someone will call them pro-crime or a lawyer will try to use the reduction in lighting as the cause for an accident; even though no court has or will consider this as having any merit. As long as the city uses a recognized lighting standard, to the best of my knowledge there has never been a case in which a judge or jury has ruled in favor of the plaintiff or awarded damages. Ever. The only lawsuits involving claims regarding lighting that have ever been won, involve improperly maintained (burned out lamps) and these too are extremely rare.

    So rather than install adaptive controls that can save 70% or more of the energy, operating costs and CO2, most cities continue to take the “safe” path. The safe path that helps contribute to wasting 1.1 PetaWatt Hours, 750 million tons of CO2 and $110 billion each year. (

    How exactly is this safe?

    Puffing yourself up because you saved half of the energy, CO2 and $$$ that you could have is like bragging that you only overpaid 35% on your new car or house instead of 70%. We’re still going to think that you’re nuts and not very fiscally responsible.

  10. How much light is enough? How much is too much?

    Until we solve this fundamental question, cities will continue to err on the side of “safety” and overlight to avoid potential litigation and public protest. Current lighting standards allow reduced illumination levels based on traffic volume and in most instances this allows significant reductions in lighting after rush hour. This is to say that using today’s standards, most cities could reduce most streetlighting by 50% or more from 9pm to dawn.

    In cities that have done this the public usually doesn’t notice the dimming and complaints are normally not based on illumination level. But turning lights off at night almost always get far more attention even when the volume of traffic doesn’t justify lighting the streets. The absence of lighting has much more to do with the “feeling of safety” than actual safety. Even though most research shows no real correlation between lighting and crime or accidents, surveys often show a very direct linkage between the feeling of safety and public lighting.

    The primal fear of the dark cannot be ignored, but can it be the basis of a sound and sustainable public lighting policy? For over a hundred years the lighting industry has trained the public and planners to equate lighting with safety in order to sell their product: you just can’t turn something like that off like a switch.

    What is the answer? First to understand why we really use public lighting and then to fundamentally change how we design the lighting to meet the public’s need and do so in a sustainable way.

    In this case, Mies van der Rohe was right: less is more. The current lighting standards for cities answer the wrong questions. It’s time to focus lighting on the needs of the pedestrians (residents), not the drivers. Headlights solve most of the driver’s visibility needs below 40mph. Pedestrian lighting that improves the quality, not quantity of illumination needs to be considered first. Glare-free, warm color temperature community friendly pedestrian lighting is what residents actually want but unfortunately can seldom articulate to planners.

    Instead for a century cars have gotten all the attention. We light the roads for them and spill a bit of light onto the sidewalks so people don’t trip over curbs. When cities do use pedestrian scale lighting fixtures they often choose the worst possible fixtures (acorns) and try to make them bright enough to light the streets as well. This results in the worst possible compromise: outrageous glare, invasive light trespass and poor quality lighting.

    To make matters worse as cities make the transition to LED, they often decide that using cool, blue-rich white light will save more energy and install it without asking the neighborhoods that will have to live under it. When asked and shown the difference in demonstrations, residents almost always vote for warmer glare-free streetlights that eliminate light trespass. Energy efficiency is a big factor but making neighborhoods look like parking malls is not the way to achieve it. Pedestian-focused, adaptive controls and sensible dimming and curfews will save far more energy and improve the quality of life at the same time.

    So all we have to do is reform lighting standards and undo a century of “more lighting makes you more safe” indoctrination by the police and lighting manufacturers. Easy right?

  11. Here’s a link to an article that describes the ability to assess the total quantity of energy used by a city using a new satellite ( The researchers have determined that US cities are three to five times brighter than their equivalents in Germany. The research will now try to understand why the US uses so much more light at night. I can give them a head start: lawyers and advertising.

    Cities in the US are over lighted due to concerns for safety. For decades the typical lighting design for street and area lighting has been lighted in excess of IES recommended practices to ensure that if there is an accident they won’t lose a lawsuit.

    SOLA has estimated that overlighting accounts for 25% of all energy waste of outdoor lighting (, but it now appears we may have been off by a substantial percentage.

    The second factor is advertising with light. Businesses in the US learned early that using outdoor lighting makes their location appear safe and appealing, thereby attracting more customers. With no limits on the quantity of Illumination being used, many businesses abuse this practice and overlight in order to compete for customers. We call this the “lumen wars”. Gas stations and convenience stores have long engaged in these battles and communities and the night sky have been the casualties.

    As my previous blog entry discussed; how much is too much? When is it enough? Until we use scientific research as a basis for recommendations we will not know. Current recommended practices for lighting levels are often based on consensus, not vision science.

    Once we do all the research, it will not address the public’s fear of the unknown or the “perception of safety” that lighting provides.

    Finally unless cities are willing to enact lighting standards that specify a limit on the quantity of lumens that can be used, this problem will never be addressed. The IDA and IES created a Model Lighting Ordinance in 2011 that included liberal caps on illumination levels (, and four years later only a handful of cities have adopted it. I estimate that 99% of all lighting ordinances currently in effect have no mechanism to control the quantity of light being used. As long as the fear of dark trumps the cost of energy, the US will continue to waste billions of dollars and millions of tons of carbon each year.

  12. The Psychology of Outdoor Lighting

    Why do we light at night? Easy, to see. Right?

    Why do we overlight? To see better? Nope. We overlight in order to feel safer.

    How much light would we need to really feel safe? Daylight?

    Do you feel completely safe walking down an alley during the day?

    So even broad daylight won’t make us all feel 100% safe; what point do we pick between no light and sunlight where we can see to safely navigate without spending more money than we have and turning night into day? Answer: Depends on whom you ask.

    While this is the question we need to ask, it seems like nobody really wants to know. It would help to ask the best vision scientists to do the research without any outside pressure or pre-conceived ideas. Vision and visibility are about as complex as it gets, but the talent is out there to define what is needed to see well. All we need is for somebody that cares enough to pick up the tab.

    My conversations with the best and brightest over the years have been “illuminating”. It turns out that our current lighting standards not only are not science-based, the metrics being used don’t even ensure maximum visibility. Illumination levels and uniformity have served as the core of most lighting standards for the last 50 years or so, but contrast, not brightness is how we actually see. However because contrast is much harder to define and measure, standards have used easier metrics. Metrics that have only recently included glare, the single factor that can degrade visibility the most. Again, glare is difficult to measure and there is still no accepted metric for it.

    Until we better define how much illumination and of what type is necessary for visibility, we will continue to overlight. But even if we were able to quantify the lumens necessary and define the perfect metric tomorrow, would we revise lighting standards to specify illumination levels that were half or a tenth of what is currently being specified?

    The very mention of dimming to match current recommended practice illumination levels late at night is often met with public protest. In the UK where “switch-offs” have been implemented when lighting was found to be unnecessary for safety, communities have petitioned and convinced elected officials to turn them back on. Bear in mind that these are often communities that had turned them off due to dire budget situations and the choice was lighting or laying off police or firefighters. Some might argue that police and firefighters contribute at least as much as streetlights to public safety.

    From the start, lighting policy has always been an emotional issue. Edison sold street lighting on a promise of improved safety, without any evidence to back up the claim. After 100 years of repeating the message, is it any surprise that the public equates brighter with safer? Educating the public on how much light is enough will require a lot of research data and years of unlearning.

    But it needs to start ASAP. We stand on the verge of a complete transformation of public lighting using LED and if we don’t figure it out soon we’ll live with the energy waste and increased CO2 for another 20 or 30 years. Lighting policy should be driven by visibility and sustainability, not primal fear. We can never light our streets bright enough for people to feel completely safe and we now know that the increased levels of light at night are actually detrimental to our health and the environment. It’s time to borrow/modify the physicians motto; “Do less harm”. Balance is sorely needed and new technologies are ready to make it happen. All we need is the will to change and a whole lot of education.

  13. Here a copy of a post that I recently made to a Lighting Forum on LinkedIn on insect attraction to LED (

    I did a lot of research on this for a US NPS and Florida FWS contract while at the International Dark-Sky Association and can provide links to the best research I have found.

    In general, different species of insects are attracted to slightly different spectra, but a broad comparison of all lighting technology in use shows that most species are attracted the most to light sources that have some UV. Metal Halide wins this category by a landslide but florescent and HPS rank high as well. In comparing LED to other sources, LED is less attractive generally than these other sources. The higher the blue SPD of white LED the greater the attraction, but there isn’t a lot of difference between 6,500K and 3,000K CCT LED.

    True red LED is the winner for least attraction, followed by true amber LED, phosphor converted (PC) amber LED and LPS. Our advisory board member Travis Longcore is currently working with Philips to fine tune white LED to be less attractive by selectively “dialing out” different frequencies and cutting out the blue altogether. Here’s a link to an article on his current research.

    The key lesson with insect attraction is that the quantity of light matters equally. For instance, if there are two identical spectra lamps of different lumen output, more insects will seek out the higher lumen source. But a high lumen source of 3,000K CCT LED may outdraw a lower power HPS or incandescent.

    Our conclusion was that while true red LED was optimum, the visibility was too poor for most situations. True amber was the best choice when is efficacy was not critical and PC amber was the best for general purpose area lighting when efficacy was a priority.

    As far as the comment that 4,000K CCT is the best general purpose area light source; that is a matter of opinion and not backed up with most consumer preference testing to date. If given a wide range of SPD options, 3,000K CCT or lower is the most popular when the choices are 3,000K, 4,000K, 5,000K & 6,500K CCT. Preference is also influenced somewhat by geographic area, with northern latitudes favoring slightly cooler 4,000K CCT in some but not all cases.

    However recently when the general public in Davis, CA were polled they chose 2,700K CCT by an large margin. This report has the most recent and largest sample group for LED color temperature preference:

    The residents were so unhappy with the 4,000K CCT LED fixtures that were installed, they protested and forced the city to replace the 650 fixtures at a cost of $350,000.

    4,000K CCT is currently being installed more than any other color because it is considered by many decision makers as the best compromise between ambiance and efficacy. I believe the best choice is to provide what the public favors after conducting a preference survey. The other factors that must be considered equally are the glare and light trespass produced by the fixture. The best solution will reduce energy consumption, save money, improve visibility and enhance visual comfort.

    Bob Parks
    Smart Outdoor Lighting Alliance (SOLA)

  14. A copy of comments I posted to the Lighting Talk forum on LinkedIn .

    Regarding blue-rich white light in classrooms or interior spaces: Proper circadian cycle regulation actually needs strong blue-rich white light during the day, reduced levels in the evening and none at night. Interior office spaces have been lit using daylight white florescent for years to help simulate exterior lighting. This actually help improve alertness in spaces without natural light.

    The future of interior lighting is adaptive fixtures that regulate the blue SPD in sync with the time of day to minimize circadian disruption.

    Regarding the color temperature for exterior lighting: The use of high-blue SPD outdoor lighting is less about the impact of the light on humans and more about the rest of species that can’t control their environment. Humans should not have to put shades over their windows to sleep well but animals can’t. Saying to wait for the experts to weigh in sounds familiar. That’s what the climate change deniers are saying in the US now. The little research that has been funded on the impact of light at night all confirms that using broad-spectrum white light in the natural environment has a profound impact on all species. It changes predation, feeding and migration patterns causing winners and losers. Some species adapt to light at night and thrive, others become victims and die off.

    There is no research that I know of that has found any positive ecological benefit to a transformation to white light in the nocturnal environment. Humans may like it better, but disregarding the ecological consequences of human development gave us polluted water and air.

    We need to continue the research on light at night but install lighting now that minimizes the negative impacts that we already have good data on. HPS may not have been popular, but it is remarkably coincidental that it was about the perfect spectrum to minimize circadian disruption. I believe the ideal solution is an LED adaptive fixture that starts at dusk at 3,000K CCT and transitions to 2,000k CCT using PC amber by 11pm while dimming to meet recommended lighting levels for the specific time of night. Areas with little or no traffic should be able to be dimmed to 20% or turned off by midnight.

    We could save billions of dollars, reduce millions of tons of CO2 and reduce ecological damage to the environment ( A win, win, win solution with no losers.

  15. New contribution to the Lighting Talk forum:


    I read your beautiful publication several months ago and I want to compliment ARUP on producing it. ( It identifies a lot of important issues and towards the end tries to touch on some of the negative aspects of light. I appreciate the inclusion of light pollution and circadian disruption in the publication but it seems to be included without really being integrated into your overall lighting philosophy.

    Mark Major, who is on our advisory board, contributed an amazing design for the Olympic Park in London. His TED talk on Lighting is a must see for lighting designers. ( It articulates a new design sensibility that if adopted will achieve much of what your publication champions while reducing light pollution and light trespass.

    However the glaring omission of any mention of the ecological impact of light at night in the publication was profoundly troubling to me. “Rethinking the Shades of Night” is so human biased that it reinforces the opinion that we should do whatever is good for humans and not give a second thought about the thousands of other species that share the planet with us. Designers that create lighting that attracts and kills birds or disrupts the ecosystem of other animals need to be aware of the ecological impact of the work that they create.

    A few years ago Rafael Lozano-Hemmer put on a searchlight art installation in Philadelphia ( that epitomized the lack of understanding and concern for the nocturnal environment that some lighting designs exhibit. Only after conservation groups expressed outrage were changes made to minimize negative impacts of the project on migratory birds. (

    Earlier the World Trade Center memorial tribute lighting installation trapped thousands of birds as they became attracted to the beams of light.

    Light possesses powerful properties and the use of outdoor lighting to satisfy commercial interests needs to be balanced with ecological consequences. Designers should adopt a “Do less harm” creed and proactively ensure that their work will minimize ecological impact.

    Bob Parks
    Smart Outdoor Lighting Alliance (SOLA)

  16. Yesterday researchers in the UK have published a report commissioned by several city councils after switching some streetlights off to save money.

    The results of the report support the decision by the councils and showed that there was no negative impacts found relating to crime or traffic accidents from the switch offs. The study covered a large geographic area and the study period was over 13 years. Both of these factors are important and no previous studies that I am aware of were able to analysis this quantity of data.

    This report has potentially enormous implications for cities worldwide and reinforces the position SOLA has actively promoted. Many cities are extremely reticent to even follow internationally recognized lighting standards when they recommend reduced levels of illumination for fear of public backlash and/or potential litigation. For this reason many new LED streetlight installations do not use adaptive controls (NYC, LA, Chicago, Detroit, etc.) and billions of dollars are wasted and millions of tons of CO2 are needlessly created. (

    What isn’t solved by this new research is the widespread public perception that more lighting increases safety. The feeling of safety and real safety are not the same thing. This news article shows how difficult it will be to change the public’s perception:

    Even facing clear evidence that the lighting is not needed, this campaign wants more lighting to increase the feeling of safety and believes that it is the right of the public. In some areas of the UK petitions to turn streetlights back on have been successful and we are lighting to see these efforts continue even after this new study clearly shows that the lighting isn’t necessary for safety.

    It isn’t surprising that the public continues to equate more light with more safety, public safety campaigns have drilled this message into them for decades. What is needed now is an equally robust public outreach campaign to explain why dusk to dawn lighting is no longer needed and what the ecological impact of it is.

    Changing the innate fear of the dark that many experience will be daunting, but we will not be able to realize goals like CO2 reduction and energy conservation if governments are not willing to bridge this gap. Public lighting is an emotional issue but an informed citizenry is absolutely the best prospect for transforming public lighting policy to an energy efficient future.

  17. Here’s a comment I made today on the Lighting Talk forum of LinkedIn:


    Thanks for your excellent comments and perspective. Public lighting needs to evolve to become as ecologically responsible as it possibly can be while still meeting the needs of the community. To do so we need to stop conflating more light with more safety. Lighting doesn’t provide safety, it provides the feeling of safety. The recent UK study finally puts the erroneous assertion that lighting is a panacea for crime in the wastebasket. Good quality lighting can help law enforcement do their job, but community policing, education and economic opportunity are some of the elements that contribute to real safety.

    As you rightly identified, the primary purpose of public lighting is to enhance visibility and promote economic activity after dark. We need to start lighting public spaces for visibility without becoming fixated with illumination levels and arbitrary uniformity standards. The eye sees using contrast, both luminance and chrominance. Lighting that introduces glare in order to meet uniformity goals defeats the basic function of lighting.

    The eye is incredibly adaptive and we can see well under much lower illumination levels if glare is eliminated. But over the last couple decades I have seen too many cities using acorn fixtures with very high lumen output and high levels of glare. Using these fixtures that were originally designed for <1000 lumen light sources with 5 to 10 times this output is just plain wrong. The best optics available for these fixtures still put too much light in the the user's eyes. This creates a escalation spiral where you then need more lumens to illuminate the target surface to compensate for the glare.

    Lighting standards need to be overhauled to emphasize contrast, reduced glare and scientifically develop new metrics using what vision scientists have learned over the last couple decades.

    We also need to include dimming controls in all public lighting, especially streetlights. All technical lighting standards in common use specify illumination levels based on the volume of pedestrian and vehicle traffic. When the volume decreases, the illumination levels specified is reduced as well. While older technology wasn't up to dynamically adapting to meet these reduced levels, SSL can and not using it is emblematic of a society's unwillingness to reduce lighting levels. Since the industry has used safety as a key sales tool for the last century, the public has learned to equate more light with more security. So reducing lighting levels is automatically considered a reduction in safety. As it took decades to train the public that lighting equals safety, it will be hard to wean them off of it. But by using today's existing technical standards, we can reduce illumination levels by 50% or more after rush hour and save the equivalent money, energy and CO2. When lighting is no longer needed, the highest energy efficiency can be achieved by turning fixtures off.

    Another technology on the horizon that will become viable in the near future is dynamic spectral tuning. It is being used in interior lighting design but hasn't made the transition to exterior. LED fixtures can easily integrate several banks of different CCT LEDs with separate drivers. During rush hour we could use 3500 K CCT for maximum visual acuity and transition to 2200 K CCT by 9 pm. In ecologically sensitive areas a bank of PC amber LEDs could be used for the duration of the evening while being dimmed to minimize the negative impact of LAN on the nocturnal environment.

    While we no longer have many technological limitations, I'm afraid that our technical standards and the primal fear of the dark will limit our ability to employ it most efficiently. If so we will miss an important opportunity to save vast amounts of money, energy and CO2 over the next decade and we'll be stuck with these installations for several decades to come.

  18. Here’s my comments on a discussion of street lighting at

    Bob Parks, LC, MIES to Meg Smith:

    Spot on Meg. The biggest threat to outdoor lighting is the lack of design skill within most DOTs and their institutional reticence to hire consultants to help them. The LED revolution pushed them out of the comfort zone that they enjoyed for the last 50 years and they continue to design by the numbers. That’s why they care little about the lighting quality and ambience of the neighborhood. I see the lighting color temp in urban lighting issue as much about the ambiance of the community.

    DOTs have always installed whatever is the most efficacious light source and given their priorities we saw them embrace >6000K CCT initially and only recently has ~4000K CCT become normal. If they cared about customer service they would allow the community to express their color temperature preferences. When you actually do ask, the majority of the public they prefer <3000k CCT. Recently in Davis, CA the public chose 2700K CCT and to reduce illumination levels by 25%.
    Quality of life matters.

    Bob Parks, LC, MIES to Glenn Heinmiller:

    Glenn, I totally agree that excess light levels are still the biggest problem in public lighting today and DOTs resistance to using smart controls to dim to maintain proper RP-8 illumination levels is completely unsupportable. As you showed in Cambridge, MA ( if you are serious about saving money, energy and CO2 you need to break the cycle of over-lighting to perpetuate the myth that it reduces crime. There is zero data to support the myth but the fear of litigation continues to dictate public policy. When will planners say enough and fully embrace the standards that they profess to base their lighting design on. The kicker is that there is also no evidence that any litigation based on illumination levels has ever resulted in a legal judgment against a municipality. Ever. Anywhere.

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